Use of geopolymeric additive in combination with non-brominated flame retardant in polymer foams

ABSTRACT

The invention relates to the use of i) geopolymer and ii) non-brominated, phosphorus- and/or nitrogen-based flame retardants for improving the self-extinguishing properties of a composition comprising polymer. The polymer may be a vinyl aromatic polymer, and may be in a granulate or foam.

The present invention relates to the use of i) geopolymer and ii)non-brominated, phosphorus- and/or nitrogen-based flame retardantsselected for improving the self-extinguishing properties of acomposition comprising polymer. Further, the invention relates to aprocess for the production of expandable polymer granulate by anextrusion or a suspension process, preferably wherein the polymer is avinyl aromatic polymer. Moreover, the invention relates to a compositioncomprising polymer, the composition further comprising i) geopolymer andii) non-brominated, phosphorus- and/or nitrogen-based flame retardants.

Vinyl aromatic polymers are known and are used for the preparation ofexpanded products that are adopted in a variety of applications, ofwhich the most important one is for thermal insulation. This is whythere is a continuously increasing demand for expanded vinyl aromaticpolymers with low thermal conductivity as well as good mechanical andself-extinguishing properties.

Hexabromocyclododecane (HBCD) has been used as a flame retardant invinyl aromatic polymer foams for many years. Only very small quantitiesof HBCD are needed to meet the self-extinguishing standards. In vinylaromatic polymer foams, such as expandable polystyrene, the requiredfinal concentration is in a range of from 0.5 to 1.0 wt. %. However,HBCD was recognized as Substance of Very High Concern and was placed bythe European Chemical Agency onto the SVHC list (decision of 28 Oct.2008). Also, HBCD has been found widely present in biological samplesfrom remote areas, and there is supporting evidence for itsclassification as persistent, bioaccumulative and toxic (PBT) and thatit undergoes long-range environmental transportation. Due to itspersistence, toxicity, and ecotoxicity, the Stockholm Convention onPersistent Organic Pollutants (POPs) decided in May 2013 to include HBCDin the Convention's Annex A for elimination, with specific exemptionsfor expanded and extruded polystyrene in buildings, which was needed togive countries time to phase-in safer substitutes.

In the meantime, a much more environmentally sustainable alternative toHBCD has been implemented by polystyrene foam producers, namely abrominated polybutadiene block copolymer (polymeric brominated flameretardant, pFR) which is now available on the market. Compared to HBCD,pFR exhibits a more sustainable health, safety and environmentalprofile. High molecular weight polymeric additives have inherentlybetter environmental and health risk profiles and often provide a moresustainable solution than smaller molecules. Nevertheless, bromine ispresent during the production and in the final use of the pFR. Also,bromine production and bromination processes themselves are recognizedas very pollutant for the environment and toxic for humans. Moreover,even though bromine as incorporated into the polymeric foam as pFR isnot eluted, it can be found in the environment after tens or hundreds ofyears, due to degradation of the polymer matrix if exposed to thedegenerative activity of the sun's UV radiation, humidity, air, andwater. The same problem is associated with other polymeric materialswhich are self-extinguished by brominated macro- or simple molecules andare exposed to the environment. Finally, halogenated FRs, in particularbrominated FRs, have limited thermal stability, which puts constraintson the processing of the compositions to which they are added.

Elimination of brominated flame retardants for use in polymers ingeneral is the only sustainable way to produce more environmentally andhuman-friendly products which are not persistent, bioaccumulative andtoxic. One of the solutions is the use of earth minerals in combinationwith phosphorus- and/or nitrogen-based flame retardants, but theirefficiency in flame suppressing is very low and a high loading isnecessary to achieve the desired flame retardancy. Such synergisticcompositions are widely known from the car or cable industries.

Due to the efforts to reduce the loading of e.g. polystyrene foams withbrominated flame retardant, and thus efforts to prevent the productionof toxic gases and a high level of smoke during combustion, theattention focuses on non-halogenated flame retardants. A variety ofphosphorus-containing compounds is used and maintains a high level offire safety.

The function mechanism of phosphorus flame retardants varies, dependingon the type of chemical structure of the phosphorus compound and itsinteraction with the polymer or the other additives during pyrolysis.Also, the flame retarding action may be optimized using a synergisticcompound. The interaction may take place according to both physical andchemical mechanisms and may occur in the condensed or in the vapourphase. Often, two or more different mechanisms are involved in givensystems.

In the condensed phase, the phosphorous-containing additives catalysethe clipping of polymer chains, thereby reducing polymer molecularweight and resulting in a decrease of viscosity, causing consequentlyheat loss due to dripping. Furthermore, phosphorus acts due toacid-catalyzed dehydratation and char formation, providing thermalinsulation for underlying polymer and preventing fuel release. Thephosphorous-rich flame retardants cause an initial crosslinking reactionthrough the polymer, and this means that the polymer is prevented fromvolatilising (thus, less combustible species are formed). Another modeaction is via intumescence (swelling). In the gas phase, phosphoruscompounds cause radical recombination as well as replacement of hydrogenand hydroxyl radicals by other, less effective radicals, thus inhibitingcombustion. Examples of commercially available phosphorus- andnitrogen-containing flame retardants are ammonium polyphosphates (e.g.Exolit 462), melamine phosphates (e.g. Melpur 200), triphenylphosphate(e.g. Disflammol TP), bisphenol A bis-(biphenylphosphate) (e.g. FyroflexBDP), and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (e.g.STRUKTUROL).

Nitrogen compounds are characterised by low toxicity and relatively lowrelease of smoke during fire, as well as a high decompositiontemperature, which is an advantages for thermoplastic polymers that areprocessed via extrusion or injection moulding.

The interaction mechanism is usually physical, although a chemical modeof action is also known. Nitrogenous agents like melamine cyanurate ormelamine undergo sublimation at ca. 350° C., whereby a significantamount of thermal energy is absorbed. Degradation of cyanuric acid alsocosts energy which consequently leads to decrease of the temperature inthe fire zone. At higher temperature, the decomposition of melamineresults in the elimination of ammonia and the formation of inert gases.Oxygen or other combustible gases dilute in inert gases, whichconsequently results in the formation of thermally stable condensates.Melamine as well as it salts promote dripping, resulting in thewithdrawal of fuel. Melamine compounds are usually used together withother flame retardants offering synergistic effects, and such an effectwith phosphorus based formulations is well known. Melamine, melaminecyanurate and other melamine salts and compounds are currently the mostused group of nitrogen-containing flame retardants.

Unfortunately, a high concentration of mineral or phosphorus- ornitrogen-based flame retardant very much deteriorates the generalproperties of polymer foams. This is why brominated FR's have been usedfor decades in vinyl aromatic polymer foams. Their high effectivity inthe gas phase, thus relatively low concentrations (up to 3 wt. %), givesan enormous advantage in the self-extinguishing of vinyl aromaticpolymeric foams. Up to know no better solution has been found.

EP 1 997 849 A1 teaches inorganic materials as binder coating onexpandable or expanded polystyrene beads or particles. The disadvantageof coated beads is that foam having a with very high density (of above70 kg/m³) is formed, because the coating has to be with a high loading,such as 80% by weight or more. Such foams also suffer from a high wateradsorption, and only interior applications are possible. Moreover, foamsprepared from coated beads have a high stiffness, which results inproblems during cutting. Because the coating is applied onto beads, soone needs specific mixers and special moulds. Consequently, thistechnology is not applicable for current customers equipment, andresults in foams having limited applications.

WO2008/113609 A2 discloses geopolymer compositions and coatings preparedtherefrom.

Furthermore, WO 2016/113321 A1 teaches that the addition of geopolymeror its composite as prepared with various types of athermanous additivesmakes it possible to maintain the polymer foam's self-extinguishing andmechanical properties in the same range as in an expanded polymerwithout addition of filler or any other athermanous additive, while atthe same time the thermal conductivity can be decreased significantly.This is possible because the geopolymer itself gives fire resistance,and further encapsulates the particles of athermanous additive,especially of those additives that are based on carbon or mineral, andseparates them from any disadvantageous interactions with the flame, thepolymer, or the flame retardant. The presence of geopolymer furtherdecreases thermal conductivity, because of its own heat radiationscattering effect.

Geopolymers are inorganic amorphous polymers with a three-dimensional,crosslinked alumina silicate structure, consisting of Si—O—Al—O bonds.The structure may be created in a sol-gel method by metal alkaliactivation of alumina silicate precursors. The formed gel productcontains alkaline cations which compensate for the deficit chargesassociated with the aluminium-for-silicon substitution. During thedissolution of alumina silicate precursor and gel formation, anintermediate, aluminium rich phase is first formed which then gives wayto a more stable, silicon-rich product. Under these conditions, freeSiO₄ and A10₄ ⁻ tetrahedral units are generated and are linked to yieldpolymeric precursors by sharing all oxygen atoms between two tetrahedralunits, while water molecules are released. The tetrahedral units arebalanced by group I or II cations (Na⁺, K⁺, Li⁺, Ca²⁺, Ba²⁺, NH₄ ⁺,H₃O⁺, which are present in the framework cavities and balance thenegative charge of Al³⁺ in tetrahedral coordination, i.e. A10₄ ⁻). Thismaterial was early investigated and developed by Davidovits aftervarious catastrophic fire incidents in France in the 1970s. The term“geopolymer” was coined in view of the transformation of mineralpolymers from amorphous to crystalline reaction through a geochemicalprocess at low temperature and short curing time. Geopolymers arerepresented by the general chemical formula ofM_(n)[—(Si—O₂)_(z)—Al—O]_(n).w H₂O, in which M is an alkali metal, z is1, 2 or 3 and n is the degree of polymerization. Based on the Si/Almolar ratio, three monomeric units can be defined: polysialate (Si/Al=1;Si—O—Al—O—), polysialatesiloxo (Si/Al=2; Si—O—Al—O—Si—O—) andpolysialatedisiloxo (Si/Al=3; Si—O—Al—O—Si—O—Si—O—.

The structure of geopolymers can be amorphous or semi crystalline,depending on the condensation temperature. Amorphous polymers areobtained at 20-90° C., whereas semi-crystalline polymers are obtained inthe range 150-1200° C. This class of materials demonstrates ceramic-likeproperties, including extreme fire resistance. Geopolymers can beamorphous or crystalline materials. They possess a microstructure on ananometre scale (as observed by TEM and measured by mercury porosimetry)which comprises small aluminosilicate clusters with pores dispersedwithin a highly porous network. The cluster size is typically between 5and 10 nm. The synthesis of geopolymers from aluminosilicate materialstakes place by the so-called geopolymerization process, which involvespolycondensation phenomena of aluminate and silicate groups, withformation of Si—O—Al type bonds. WO2015/191817 A1 teaches geopolymeraggregates and their use in a variety of applications.

US 2008/0 249 199 A1 teaches a method for the manufacture of foamed orfoamable particles from a polymer melt. A recycled polymer melt isintroduced into the polymer melt through a side extruder and may includeadditive. This is said to be more economical than the use of amasterbatch. If bromide-containing flame protection agents or otherthermally unstable additives are present in the recycled polymer, or areadded to the recycled polymer, the process temperature in the sideextruder and in all following system components should not exceed atemperature and dwell time limiting value which is defined by thethermal stability of the additives.

WO 2006/058733 A1 teaches expandable styrene polymer granulatescontaining a) athermanous additive selected from the group of inorganicpowder materials such as silicic acid and b) carbon black or graphite.Further, EP 0 863 175, EP 0 981 574, EP 1 758 951 and EP 1 771 502 A2teach the use of graphite in polystyrene foam obtained by an extrusionprocess.

WO 2006/058733 also teaches that the mechanical properties ofthermoplastic polymers containing fillers can be improved by usingadhesion promoters (coupling agents), such as maleic anhydride modifiedstyrene copolymers, epoxy group containing polymers, organosilanes orstyrene copolymers having isocyanate or acid group. Similar to US 2008/0249 199 A1, WO 2006/058733 A1 also proposes to use side extruders forintroducing additives such as solids and thermally sensitive additives.This arrangement is, however, undesirable in situations where additivesthat are not thermally sensitive, but rather require thorough mixing,are to be introduced. This is because large amounts of material wouldneed to be processed if additives that require thorough mixing were tobe introduced into a main portion of the polymer. This is economicallyundesirable. The addition of dedicated coupling agents is likewiseundesirable, especially if they need to be used in large amounts.

WO 2004/087798 A1 teaches expandable vinyl aromatic polymers comprising,in a polymer matrix, a type of carbon black having an active surfacearea ranging from 5 to 40 m²/g. The thermal conductivity of a materialwith a density of 14 g/l is reported to be 36.5 mW/m*K.

WO 2006/061571 A1 teaches an expandable polystyrene compositioncomprising carbon black as an additive, the carbon black having a veryhigh BET surface, as measured according to ASTM D 6556, ranging from 550to 1,600 m²/g. The examples report polystyrene foam with a thermalconductivity of 36.16 mW/m*K at density 13.3 g/l according to ASTM D1622, and 34.21 mW/m*K at density 19.4 g/l, respectively.

WO 2008/061678 A2 discloses the use of carbon black having a specificelectric conductivity, to reduce the thermal conductivity of expandablevinyl aromatic polymers. The carbon black is introduced duringsuspension polymerization, or during polymer extrusion. The examplesreport polystyrene foam having a thermal conductivity of 31.0 mW/m*K ata density of 17 g/l.

Japanese patent JP 63183941 teaches the use of aluminium pigment,titanium dioxide and graphite, having specific particle size and heatradiation reflectivity, to reduce the thermal conductivity ofpolystyrene foams. Examples 7 to 11 teach polystyrene foam produced byan extrusion process and having a thermal conductivity of 25 to 30mW/m*K, where masterbatches were used as starting material.

WO 2005/123816 A1 teaches styrene polymer particle foam materials. WO2004/087798 A1 teaches expandable polystyrenes containing carbon black.In a suspension polymerization process, the carbon black is presentduring the polymerization in aqueous suspension. Also disclosed is acontinuous process for preparing expandable polystyrene in mass, whereinthe polymer is fed together with carbon black into an extruder, and,subsequently, expanding agent and possible further additives areinjected into the molten polymer before extrusion through a die.

WO2010/128369 A1 teaches thermoinsulating expanded articles comprisingan expanded polymeric matrix, obtained by expansion and sintering ofbeads/granules of a vinyl aromatic (co)polymer, in whose interior afiller is homogeneously dispersed, which comprises at least oneathermanous material selected from coke, graphite and carbon black andoptionally an active inorganic additive within the wave-lengths rangingfrom 100 to 20,000 cm⁻¹.

US2012/264836 A1 teaches nanocomposite compositions based on expandablethermoplastic polymers which comprise: a) a polymeric matrix, b)expanding agent englobed in the polymeric matrix; c) athermanous fillercomprising nano-scaled graphene plates having specific dimensions.

US 2008/0028994 A1 entitles “Geopolymer Compositions and Application inOilfield Industry” teaches a geopolymer composition formed from asuspension comprising an aluminosilicate source, a metal silicate, analkali activator, and a carrier fluid. Lightweight particles and/orheavyweight materials may be added to control density of thecomposition. Barium sulphate or ilmenite are examples for heavyparticles.

WO 2010/141 976 A1 entitles “Concrete Aggregate” discloses polymericaggregates produced from fly ash combined with an activator. Theaggregate is used in concrete, mortar, or road base. WO2009/009089 A1discloses a process for treating fly ash to render it highly usable as aconcrete additive.

It was the object of the present invention to provide improved flameretardants for polymers, for instance vinyl polymers, in particularvinyl aromatic polymers, especially when they are in the form of foams.These flame retardants should not necessarily comprise bromine, andshould not deteriorate mechanical and other properties of the polymersto which they are added.

It has surprisingly been found that this object is solved in accordancewith the present invention by the use of

-   i) one or more of    -   a) a geopolymer;    -   b) a combination of a geopolymer with an athermanous additive;        and    -   c) a geopolymer composite derived from geopolymer and comprising        athermanous additive,-   and-   ii) one or more non-brominated flame retardants selected from    -   a) phosphorus-based flame retardants,    -   b) nitrogen-based flame retardants, and    -   c) phosphorus/nitrogen-based flame retardants.

The addition of i) geopolymer, geopolymer in combination withathermanous additive, or geopolymer composite as prepared with varioustypes of athermanous additives and ii) non-brominated phosphorus- and/ornitrogen-based flame retardants in relatively small concentrations incompositions comprising polymer makes it possible to maintain thecomposition's self-extinguishing properties, without the need forbrominated flame retardants. Indeed, and if desired, the presence ofbrominated flame retardants can completely be dispensed with. This ispossible because the geopolymer synergistically interacts withphosphorus- and/or nitrogen-based flame retardants.

According to the present invention, additives i) and ii) areincorporated into the polymer compositions as fillers. These additivescan be used in typical compounding technology which is common for allthermoplastic polymers. This is in contrast to the teaching of EP 1 997849 A1, where an inorganic material is used as a binder coating onexpandable or expanded polystyrene beads or particles.

According to the present invention, the water content of the final(modified) geopolymer or (modified) geopolymer composite used/producedis preferably in a range of from 1 to 50 wt. %, preferably 2 to 30 wt.%, more preferably 3 to 20 wt. %.

(Modified) geopolymer or (modified) geopolymer composite used accordingto the present invention may be used together with brominated flameretardant. Because brominated flame retardants have limitedcompatibility with products having a certain sodium content, the sodiumcontent of the (modified) geopolymer or (modified) geopolymer compositeis preferably less than 5000 ppm, more preferably less than 500 ppm, inparticular less than 200 ppm, such as less than 100 ppm, or even lessthan 50 ppm, each calculated on dry mass.

If the (modified) geopolymer or (modified) geopolymer compositeused/produced according to the present invention is not used togetherwith brominated flame retardant, then the sodium content need notnecessarily be low. In this embodiment, the sodium content of the(modified) geopolymer or (modified) geopolymer composite is preferablyless than 50,000 ppm, more preferably less than 10,000 ppm, inparticular less than 5,000 ppm, each calculated on dry mass.

At the same time the thermal conductivity can be decreased. The presenceof geopolymer decreases thermal conductivity, because of its own heatradiation scattering effect and influence on surface modification ofcarbon particles phase.

The present invention has the following aspects:

-   I) The use of i) one or more of a) a geopolymer; b) a combination of    a geopolymer with an athermanous additive; and c) a geopolymer    composite derived from geopolymer and comprising athermanous    additive, and ii) one or more non-brominated flame retardants    selected from a) phosphorus-based flame retardants, b)    nitrogen-based flame retardants, and c) phosphorus/nitrogen-based    flame retardants.-   II) A process for the production of expandable polymer granulate by    an extrusion or a suspension process, wherein the polymer is    preferably a vinyl aromatic polymer.-   III) A composition comprising one or more polymers, the composition    further comprising a) a geopolymer; b) a combination of a geopolymer    with an athermanous additive; and c) a geopolymer composite derived    from geopolymer and comprising athermanous additive, and ii) one or    more non-brominated flame retardants selected from a)    phosphorus-based flame retardants, b) nitrogen-based flame    retardants, and c) phosphorus/nitrogen-based flame retardants.

DETAILED DESCRIPTION

I) The use of i) geopolymer or geopolymer composite derived fromgeopolymer and comprising athermanous additive, and ii) non-brominatedflame retardants selected from a) phosphorus-based flame retardants, b)nitrogen-based flame retardants, and c) phosphorus/nitrogen-based flameretardants

According to the first aspect, the present invention relates to the useof

-   i) one or more of    -   a) a geopolymer;    -   b) a combination of a geopolymer with an athermanous additive;        and    -   c) a geopolymer composite derived from geopolymer and comprising        athermanous additive,-    and-   ii) one or more non-brominated flame retardants selected from    -   a) phosphorus-based flame retardants,    -   b) nitrogen-based flame retardants, and    -   c) phosphorus/nitrogen-based flame retardants,        for improving the self-extinguishing properties of a composition        comprising one or more polymers.

Preferably, the improvement is measured according to DIN 4102 (B1, B2)and EN ISO 11925-2, more preferably the improvement is measuredaccording to EN ISO 11925-2.

Preferably, the polymer is selected from vinyl polymer, polyurethane,polyolefin, polycarbonate, polyester, polyamide, polyimide, silicone andpolyether, more preferably the polymer is selected from vinyl aromaticpolymer, polyethylene and polypropylene, most preferably the vinylaromatic polymer is polystyrene.

Moreover, it is preferred that the composition does not comprisepolymeric brominated flame retardant, more preferably the compositiondoes not comprise brominated flame retardant. It is in particularpreferred that the composition does not comprise halogenated flameretardant.

The athermanous additive as used in admixture with geopolymer, or ascontained in geopolymer composite, is one or more selected from thegroup consisting of

-   -   (1) carbon-based athermanous additives,    -   (2) metal athermanous additives,    -   (3) metal oxide athermanous additives, and    -   (4) metal sulfide athermanous additives.

Preferably, the carbon-based athermanous additive (1) is selected fromcarbon black, coke, graphitized carbon black, graphite, graphite oxides,anthracite, graphene, and graphene oxide.

The metal athermanous additive (2) is preferably selected from copper,bismuth, nickel, iron, tungsten, silver, cadmium, cobalt, tin, zinc.

The metal oxide athermanous additive (3) is preferably selected fromoxides of the metals of groups IIIB, IV-VIIIA, and I-VB of the periodictable.

As will be explained below, the geopolymer or geopolymer composite maybe modified with one or more water-soluble compounds. Preferably, thewater-soluble compound is selected from phosphorus compounds, nitrogencompounds, copper compounds, silver compounds, zinc compounds, tincompounds, and magnesium compounds, more preferably the modification iswith a phosphorus compound, in particular the modification is with aphosphorus compound selected from phosphoric acid and ammoniumpolyphosphate.

Geopolymer and Geopolymer Composite

The invention requires that geopolymer or geopolymer composite is used.Processes for the production of geopolymer are known, see e.g.WO2015/191817 A1.

In a first preferred embodiment, the geopolymer is present as geopolymercomposite. It may be produced in accordance with the process of WO2016/113321 A1, which process comprises

-   -   a) mixing of an aluminosilicate component with an alkaline        silicate solution, to form a gel,    -   b) adding of an athermanous additive component to the gel, to        form a filled gel,    -   c) mixing of the filled gel, to form filled geopolymer,    -   d) curing, drying and milling, to give filled geopolymer        particles,    -   e) optional removal of cations from the filled geopolymer        particles, and    -   f) obtaining the geopolymer composite.

In a second preferred embodiment for the geopolymer or geopolymercomposite production process, the geopolymer or geopolymer composite isproduced in accordance with the process of international patentapplication entitled “Process for the production of geopolymer orgeopolymer composite” (PCT/EP2017/068346), filed on even date herewith,the disclosure of which application is incorporated herein in itsentirety. PCT/EP2017/068346 claims priority from EP16461542.9 filed onJul. 20, 2016.

According to this alternative process, geopolymer or geopolymercomposite is prepared in a process comprising

-   a) mixing of precursor for aluminate and silicate in alkaline    solution, to form a sol-gel,-   b) optionally adding of one or more additives to the sol-gel, to    form a filled sol-gel,-   c) adding water to the sol-gel or filled sol-gel, to form a diluted    sol-gel or diluted filled sol-gel,-   d) mixing of the diluted sol-gel or diluted filled sol-gel, to form    a geopolymer or geopolymer composite,-   e) obtaining a suspension of geopolymer or of geopolymer composite,-   f) optional reduction of the content of alkali metal cation within    the structure of the geopolymer or geopolymer composite, and-   g) obtaining the geopolymer or geopolymer composite,    wherein step e) comprises    -   e1) decantation, or    -   e2) adding of an organic phase, emulsifying, and stripping of        the organic phase.

Step a) is preferably performed by mixing of precursor for aluminate andsilicate, to form a sol-gel, wherein the mixing is under alkalineconditions.

This process will in the following be described further.

In the second preferred embodiment for the geopolymer or geopolymercomposite production process, the mixing in step a) may comprise themixing of an aluminosilicate, a phosphoaluminate, an alkaline silicateand/or an alkaline aluminate. Thus, in a first step, the sol-gel isprepared, for instance from a mixture of aluminosilicate precursor andactivator such as sodium aluminate or sodium disilicate, with additionof water. It is also preferred to use sodium disilicate or sodiumaluminate or their potassium analogues. Especially, it is preferred thatthe alkaline solution is a water-diluted sodium aluminate or sodiumdisilicate, in particular sodium aluminate.

Further, it has been found that the use of a geopolymer or a geopolymercomposite prepared from a mixture of aluminosilicate precursor andphosphoaluminate further enhances the self-extinguishing effect in vinylaromatic polymer foams. Also, this improvement is achieved when thistype of athermanous and flame retarding constituent is used in otherexpandable vinyl polymers such as polyethylene and polypropylene or evenother type of polymers such as polyamides, polyurethanes, polyesters,polyimides or various types of resins.

In a further preferred embodiment, the mixing in step a) involves one ormore materials selected from the group consisting of dehydroxylatedkaolinite, metakaolin, metakaolinite, fly ash, furnace slag, red mud,thermal silica, fumed silica, halloysite, mine tailings, pozzolan,kaolin, and building residues. Particularly preferred precursors aredehydroxylated kaolinite, metakaolin or metakaolinite, but also fly ash,furnace slag, red mud, thermal silica, fumed silica, halloysite and amixture thereof.

After activation and dissolution, the ortho-sialate monomer[(HO)₃—Si—O—Al—(OH)₃] polycondensates and forms a sol-gel, so called“gel”. The mixing is in a third step c) continued. Preferably, in stepb), there is an addition of an additive, in micro or in nano powderform. During step a), b) or c), water can be introduced as a viscositymodification additive, and/or silane and/or latex as adhesion modifiers.

Changes in the Si/Al ratio can drastically affect the flexibility ofobtained modified geopolymer. According to the present invention, thesmaller the value of the Si/Al ratio, the more flexible is the modifiedgeopolymer. This was especially observed in the case of a Si/Al ratio ofabout 1, where aluminosilicates formed “more flexible” poly(sialate)structures, as compared to a 3D network of poly(sialate-siloxo) andpoly(sialate-disiloxo) exhibiting shrinkage and cracks. From theliterature, it is known that such flexibility was observed when themolar Si/Al ratio exceeds 30, with the much higher content of Si inmatrix constituents.

Mixing is typically carried out at ambient temperature, for a minimum of1 minute and a maximum of 60 minutes. In this step after the addition ofthe alkaline silicate solution (so called water glass), silane maypreferably be added to the gel, in order to improve adhesion ofgeopolymer in particular to carbon-based athermanous additives and laterto the filled polymer. The concentration of silane is preferably in therange of from 0.01 to 10 wt. %, more preferably in the range of from0.05 to 5 wt. %, most preferably from 0.1 to 3 wt. %.

Geopolymer or geopolymer composite may thus be modified by reaction withcoupling agents, to obtain better adhesion to the vinyl aromaticexpandable polymers. Different coupling agents may be used, depending onwhen the addition during the preparation of the geopolymer or thegeopolymer composite takes place. However, this depends on the type ofgeopolymer used and the type of additive within the geopolymercomposite.

-   -   Firstly, an adhesion of geopolymer or geopolymer composite to        the polymer can be improved by its in situ modification        (reaction) with silanes or organometallic titanates, zirconates        (such us Ken-React produced by Kenrich Petrochemicals Inc.). The        silane or titanate etc. can be added as weight percent per        percent of geopolymer solid mass. It can be added in the range        of 0.01-10.0 wt. % per 100 wt. % of geopolymer solid mass; in        particular 0.1-5.0 wt. %, especially 0.5-3.0 wt. %.    -   Secondly, the adhesion of geopolymer or geopolymer composite to        the vinyl aromatic polymer can be further improved by surface        modification with silane or vinyl silane of the final powder        form of prepared geopolymer or geopolymer composite. The silane        or vinyl silane can be added as weight percent per 100 wt. % of        powder. In can be added in the range of 0.01-10.0 wt. % per 100        wt. % of geopolymer solid mass; in particular 0.1-5.0 wt. %,        especially 0.5-3.0 wt. %.    -   Another opportunity for hydrophobicity improvement is butadiene        latex addition to the geopolymer gel. The resulting modified        geopolymer or modified geopolymer composite has an improved        adhesion to vinyl aromatic polymer, better dispersion of        modified geopolymer or modified geopolymer composite in the        polymer matrix, and improved mechanical properties. The        concentration of butadiene latex is preferable in the range of        from 1 to 50% wt. %, more preferable in the range of from 5 to        25 wt. %. The used latex can be butadiene copolymer latex eg.        butadiene-styrene latex (e.g. LBS 3060 S from Synthos) and        carboxylic modified butadiene latex e.g. (LBSK 5545 from        Synthos).

Whilst various silanes can be used, the best adhesion performance isachieved when using aminopropyltriethoxysilane (e.g. Dynasylan AMEO fromEvonik), aminopropyltrimethoxysilane (e.g. Dynasylan AMMO from Evonik),phenyltriethoxysilane (e.g. Dynasylan 9265 from Evonik),3-methacryloxypropyltrimethoxysilane (e.g. Dynasylan MEMO form Evonik)and vinyltrimethoxy-silane (e.g. Dynasylan VTMO from Evonik). When thesilane is e.g. 3-methacryloxypropyltrimethoxysilane, the process furtherpreferably comprises the addition of a butadiene latex in one or more ofsteps a), b) and c) (preferably, the addition of the butadiene latex isin one or more of steps a) and step b)).

Silane may also be added to the geopolymer composite in any one of stepe), optional step f) and step g). Then, the silane is preferablyselected from aminopropyltriethoxysilane, aminopropyltrimethoxysilane,phenyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, andmixtures thereof.

It is most preferred that silane is added in an amount of from 0.01 to10 wt. %, more preferably from 0.05 to 5 wt. %, most preferably from 0.1to 3 wt. %, based on the weight of modified geopolymer or modifiedgeopolymer composite.

Also, it is preferred that the additive is an athermanous additive,preferably selected from the group consisting of

-   -   a. carbon-based athermanous additives,    -   b. metal athermanous additives,    -   c. metal oxide athermanous additives, and    -   d. metal sulfide athermanous additives.

Preferably, the additive as used in combination with (preferablymodified) geopolymer or as incorporated into (preferably modified)geopolymer composite is one or more selected from the group consistingof

-   -   a. carbon black, cokes (for example a petroleum coke and/or        metallurgical coke), graphitized carbon black, graphite oxides,        various types of graphite (especially poor and amorphous forms        with a carbon content in the range of from 50 to 90%) and        graphene or graphene oxide and various types of anthracite,    -   b. titanium oxides, ilmenite, rutiles, chamotte, fly ash, fumed        silica, hydromagnesite, huntite, barium sulphate, and mineral        having perovskite structure,    -   c. metal oxides, preferably titanium oxides, iron oxides,        silicon oxides, chromium oxides, nickel oxides and more based on        metals from element table groups of IIIB, IV-VIIIA, I-VB,    -   d. metal sulfides, preferably nickel sulfide, tungsten sulfide,        copper sulfide, silver sulfide, and more sulfides are possible,    -   e. nano particles of graphite oxides and titanium oxides, iron        oxides, silicon oxides, chromium oxides, metal sulfides, metals        such as nickel, barium sulphate and component having perovskite        structure, tricalcium phosphate,        preferably the (preferably modified) geopolymer comprises one or        more carbon-based additives selected from the group of heat        absorbers and heat reflectors presented above,        in particular the carbon-based additive is carbon black,        graphite, graphite oxide, graphene oxide, coke, anthracite or a        mixture thereof.

The second and optional step b) is thus the incorporation of additives,preferably one or more athermanous additives. Preferably such additivecould be carbon black, graphite, coke, anthracite, graphite oxide.

In particular, the following cokes could be used: petroleum coke,metallurgical coke, shot coke, sponge coke, fluid coke, beaded coke,needle coke, pitch coke or anode coke.

In particular, the following anthracites could be used: greenanthracite, semianthracite, anthracite, meta-anthracite or gas calcinedanthracite and electrically calcined anthracite or dealkalized anddesulphurized types of anthracite.

Additionally, other types of carbon based additive are possible, such assea coal, graphene oxide, nanotubes or carbon fibers.

In a preferred embodiment, additive a. is selected from coke,graphitized carbon black, graphite oxides, graphite, anthracite,graphene oxide, and nano-graphite and carbon nanotubes (single andmultilayer).

Thus, in a preferred embodiment of all aspects of the invention,additive a. is selected from coke, graphitized carbon black, graphiteoxides, graphite, anthracite, graphene oxide, and nano-graphite andcarbon nanotubes (single and multilayer). Most preferred in allembodiments of the invention is that the athermanous additive is acarbon athermanous additive selected from graphene oxide, nano-graphite,and mixtures thereof.

Alternatively, metal oxides could be added, preferably, titaniumdioxide, iron oxide, chromium oxide, silicon oxide or nickel oxide ortheir nanoforms.

Further alternatively, metal sulfides such as tungsten sulfide or nickelsulfide are possible as additives.

After (optional) additive incorporation, the high shear mixing iscontinued, and further geopolymerization takes place, and additive isphysically encapsulated or chemically reacted by growing chains ofgeopolymer, thus the surface becomes modified.

The additive, or a minimum of two additives, is preferably added in anamount of from 0.01 to 80 wt. %, more preferably from 0.05 to 60 wt. %,most preferably from 0.1 to 50 wt. % depending on the type of theadditive or additive mixture, based on the weight of geopolymercomposite. Different mixtures and different ratios between the additivesare possible. After addition of additive, or mixture of at least twoadditives from the above proposed, the thixotropic gel is further highspeed mixed, to result in a homogenous consistence. Water can then beadded, to regulate the final viscosity. The water is added in apreferred ratio from 1/10 to 10/10 or depending on additive type and itsbulk density as well as hydrophilic properties and specific surface.

It is very much preferred that the process includes optionaldealkalization step f). Preferably, step f) comprises the addition of anacid solution, and subsequent drying. In particular, step f) comprisesaddition of an acid solution, washing with water, and subsequent drying.

The second preferred embodiment for the geopolymer or geopolymercomposite production process further may comprise modification with oneor more water-soluble compounds, preferably the modification is in oneor more of step f) and step g), resulting in modified geopolymer ormodified geopolymer composite, respectively. The water-soluble compoundis preferably selected from phosphorus compounds, nitrogen compounds,copper compounds, silver compounds, zinc compounds, tin compounds, andmagnesium compounds. Preferably, the modification is with a phosphoruscompound, in particular with a phosphorus compound selected fromphosphoric acid and ammonium polyphosphate.

Also, the modification of geopolymer or geopolymer composite givesmaterials having a better stability, such as improved adhesion to thepolymers into which they are incorporated. Moreover, the modificationallows one to use certain types of additives that would otherwise beunsuitable for use in expandable vinyl aromatic polymers and expandedvinyl aromatic polymer foams.

Thus, the geopolymer or geopolymer composite is produced in severalprocess steps in which if needed additive (such as coke or anthracite orgraphene oxide or metal oxide or sulfide or metal) becomes encapsulatedby chemical and physical bonding into the geopolymer matrix. This typeof geopolymer is suitable for performing a self-extinguishing action andfurther reducing the thermal conductivity properties of vinyl aromaticpolymers and expanded foam products made thereof. Additionally, it wasfound that the self-extinguishing effect could be enhanced when arelatively small amount of modifier, e.g. a phosphorus compound such asphosphoric acid or ammonium polyphosphate, is used to alter the surfaceof geopolymer or geopolymer composite. It was found that this surfacemodification can help to reduce the amount of brominated flame retardantor completely eliminate the need to use any brominated flame retardant.

Also, geopolymer or geopolymer composite suspended in water can be ionexchanged. In was discovered that, following the dealkalization in whichexchange of sodium or potassium cations by hydrogen cations is realized,or alternative to such dealkalization, an ion exchange can be performed.Such ion-exchanged particles of modified geopolymer or of modifiedgeopolymer composite (incorporating ions of Ag, Zn, Cu, Cu, Ni, Sn, Mg)further improves the reduction of thermal conductivity of polymericfoams, acting additionally as antimicrobial agent.

Final step g) of the process may thus comprise

-   -   several filtration steps, preferably two or more steps, followed        by salts washing and later repulpation in demineralized water or        an acid solution in demineralized water, while such repulpation        is followed by filtration and salts washing,    -   modification of geopolymer or geopolymer composite in filtration        and/or repulpation by a suitable acid or via ion exchange using        a suitable water-soluble salt, and    -   final repulpation of washed and/or modified geopolymer or        geopolymer composite and subsequent spray drying to obtain a        powder.

In step g), the surface modification may be performed, for instance bytreating the precipitated cake with a demineralized water solution ofacid, preferably phosphoric acid or phosphates or its salts orpolyphosphates or its salts. The surface modification by phosphorusand/or nitrogen based compounds may thus be performed with the use of anaqueous solution. The aqueous solution of the phosphorus and/or nitrogenbased compound is transferred in one or more cycles through the filterpress. If this step is needed because of the application of theresultant modified geopolymer or modified geopolymer composite, it isoften performed before the membrane squeeze and vacuum drying in themembrane filter press. The modification can alternatively be an ionexchange, with the use of a water solution of a salt such as copperchloride, silver nitrate, or magnesium sulphate, or some other saltwhich is soluble in cold or hot water.

In step e) of the second preferred embodiment for the geopolymer orgeopolymer composite production process, there are two alternatives,namely

-   -   e1) decantation, or    -   e2) adding of an organic phase, emulsifying, and stripping of        the organic phase.

In the first alternative, the process includes step e1), decantation. Inthis preferred alternative embodiment e1), the process preferablycomprises

-   -   e1a) applying high shear mixing and ultrasound with high energy,        to induce cavitation,    -   e1b) optional addition of acid, preferably addition of acid,    -   e1c) decantation,    -   e1d) optional membrane filtration, and precipitate cake washing.

In the second alternative embodiment of the process, the processincludes step e2), namely adding of an organic phase, emulsifying, andstripping of the organic phase, and the process preferably comprises

-   -   e2a) adding of an organic phase,    -   e2b) emulsifying the sol-gel,    -   e2c) applying high shear mixing and ultrasound with high energy,        to induce cavitation,    -   e2d) steam stripping to remove the organic phase, and    -   e2f) dispersion of the geopolymer or the geopolymer composite in        water, preferably deionized water.

In a third preferred embodiment, modified geopolymer or geopolymercomposite is produced in accordance with the process of internationalpatent application entitled “Modified geopolymer and modified geopolymercomposite and process for the production thereof” (PCT/EP2017/068371),filed on even date herewith, the disclosure of which application isincorporated herein in its entirety. PCT/EP2017/068371 claims priorityfrom EP16461540.3, filed Jul. 20, 2016. According to this alternativeprocess, which is based on WO2016/113321 A1, modified geopolymer ormodified geopolymer composite is prepared in a process comprising

-   -   a) mixing of precursor for aluminate and silicate in alkaline        solution, to form a sol-gel,    -   b) optionally adding of one or more additives to the sol-gel, to        form a filled sol-gel,    -   c) mixing of the sol-gel or the filled sol-gel, to form        geopolymer or filled geopolymer,    -   d) curing, drying and milling of the geopolymer or filled        geopolymer, to form particles of geopolymer or of geopolymer        composite,    -   e) optional dealkalization of the particles of geopolymer or of        geopolymer composite, to reduce the content of alkali metal        cation within the structure of the particles,    -   f) first filtration, and    -   g) second filtration,    -   wherein the process further comprises modification with one or        more water-soluble compounds,        and    -   h) obtaining the modified geopolymer or modified geopolymer        composite.

Again, step a) is preferably performed by mixing of precursor foraluminate and silicate, to form a sol-gel, wherein the mixing is underalkaline conditions.

Phosphorus- and/or Nitrogen-Based Flame Retardant

The invention further requires that, in addition to geopolymer orgeopolymer composite, phosphorus- and/or nitrogen-based flame retardantis used.

With regard to the phosphorus-based flame retardant a), it is preferablyselected from red phosphorus, organic and inorganic phosphates,phosphonates, phosphinates, and phosphoramidates. The organic phosphatemay be selected from triphenyl phosphate (TPP), resorcinolbis(diphenylphosphate) (RDP), bisphenol A bis(diphenylphosphate) (BADP),tricresyl phosphate (TCP), and resorcinol bis(2,6-dixylenylphosphate)(RDX). The phosphinate may be selected from aluminium phosphinates,calcium phosphinates and zinc phosphinates. The phosphoramidate may be9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

The nitrogen-based flame retardant b) may be selected from hinderedamine stabilizer, ammonium octamolybdate, melamine octamolybdate,benzoguanamine, tris(hydroxyethyl) isocyanurate, allantois, glycoluril,melamine, melamine cyanurate, dicyandiamide, guanidine, carbodiimides,condensation products of melamine, and derivatives thereof.

The phosphorus/nitrogen-based flame retardant c) is preferably selectedfrom melamine phosphate, melamine pyrophosphate, melamine polyphosphateammonium polyphosphate, and ethylene diamine phosphate.

Further nitrogen-containing flame retardants, phosphorus-containingflame retardants, and phosphorus/nitrogen-containing flame retardantsare disclosed in EP2899222 A1, US2004/227130A1, CN103980313 A, andCN104341612 A.

The nitrogen retardant preferably comprises condensation products ofmelamine. By way of example, condensation products of melamine aremelem, melam, or melon, or compounds of this type with a highercondensation level, or else a mixture of the same, and, by way ofexample, may be prepared by the process described in WO96/16948.

The phosphorus/nitrogen flame retardants preferably comprise reactionproducts of melamine with phosphoric acid or with condensed phosphoricacids, or comprise reaction products of condensation products ofmelamine with phosphoric acid or condensed phosphoric acids, or elsecomprise a mixture of the specified products.

The reaction products with phosphoric acid or with condensed phosphoricacids are compounds which arise via reaction of melamine or of thecondensed melamine compounds, such as melam, melem, or melon etc., withphosphoric acid. By way of example, these are dimelamine phosphate,dimelamine pyrophosphate, melamine phosphate, melamine pyrophosphate,melamine polyphosphate, melam polyphosphate, melon polyphosphate, andmelem polyphosphate, and mixed polysalts, e.g. those described inWO98/39306.

It is preferred in all embodiments of the present invention that thenon-brominated flame retardant ii) is a non-halogenated flame retardant.

Preferably, the geopolymer or geopolymer composite has an averageparticle size (D50) in the range of 0.1 to 10 μm.

II) Process for the production of expandable polymer granulate In asecond aspect, the invention relates to process for the production ofexpandable polymer granulate by an extrusion or a suspension process,the process comprising the addition of

-   -   i) one or more of        -   a) a geopolymer;        -   b) a combination of a geopolymer with an athermanous            additive; and        -   c) a geopolymer composite derived from geopolymer and            comprising athermanous additive,    -   and    -   ii) one or more non-brominated flame retardants selected from        -   a) phosphorus-based flame retardants,        -   b) nitrogen-based flame retardants, and        -   c) phosphorus/nitrogen-based flame retardants.

Preferably, the polymer is a vinyl aromatic polymer.

In the second aspect, the present invention thus relates to a processfor the production of expandable (vinyl aromatic) polymer in the form ofgranulate of so-called expandable particles (micro-pellets or beads).There are two embodiments, namely (1) an extrusion process (e.g. XEPS)and (2) a suspension polymerization process (e.g. EPS). In both types ofprocesses, incorporation of i) and ii) favourably contributes to boththe process conditions and the properties of the product.

In the first embodiment of this aspect, the invention relates to anextrusion process for the production of expandable vinyl aromaticpolymers, preferably by twin-screw extrusion consisting of a two-stepmixing of the additive and flame retardant in two twin-screw extruders.Mixing takes place in a side twin screw extruder to which the additive(modified geopolymer, or combination of modified geopolymer withadditive or mixture of additives, or modified geopolymer composite) isadded through the two side feeders, in order to better degas the meltfrom excess of water and air. In this way, a filler masterbatch iscreated “in situ” and the filled melt is then (preferably directly, i.e.as melt) transferred to the main 32D twin-screw extruder.

The main extruder is filled with general purpose polystyrene (the sameas the one dosed to the side twin screw extruder), and non-brominatedflame retardant. Then, the melt is impregnated with blowing agent(propellant, typically pentanes, or a suitable mixture). The meltcontaining all additives is then cooled in a single screw extruder. Themelt is then downstream processed in a pressurized underwaterpelletization process, to obtain vinyl aromatic polymer granulate. Thegranulate is finally coated with a mixture of zinc (or magnesium)stearate, glycerine monostearate and glycerine tristearate. If abrominated flame retardant is present, the modified geopolymer ormodified geopolymer composite preferably has a low alkali content.

According to the first embodiment of aspect (II), expandable vinylaromatic polymer granulate is preferably prepared in an extrusionprocess as shown in detail in WO 2016/113321 A1.

The use of a brominated flame retardant can in accordance with thepresent invention be reduced or even be dispensed with. Especially if nobrominated flame retardant is present, the geopolymer or geopolymercomposite as used in combination with ii) non-brominated flame retardantneed not have a low alkali content.

In the second embodiment of the fourth aspect of the invention,expandable vinyl aromatic polymer is prepared in a suspensionpolymerization process.

In the first step of a preferred suspension process, radically initiatedcopolymerization preferably takes place in the presence of powder of a.geopolymer, or b. combination of geopolymer with additive, or c.geopolymer composite, each preferably hydrophobized on the surface bythe coupling agents, in particularly by vinyl silanes. In the next step,mixing of prepolymer as obtained in first step with vinyl aromaticpolymer takes place, preferably in a twin-screw co-rotating extruder.Underwater pelletization gives a masterbatch in the form of granulate.Then, this masterbatch is preferably dissolved in styrene, together withnon-brominated flame retardant. Water is then added, followed byperoxide and surfactants. The polymerization is continued at atemperature in a range of from 75 to 130° C. Next, the resultant polymeris centrifuged to remove the water from the polymer particles(granulate), the particles are dried and are finally coated with amixture of magnesium (or zinc) stearate and/or mono- and/or di- and/ortristearate of glycerine.

The suspension process preferably comprises the steps as described inmore detail in WO 2016/113321 A1.

III) Composition

In a third aspect, the invention relates to a composition comprising oneor more polymers, the composition further comprising

-   -   i) one or more of        -   a) a geopolymer;        -   b) a combination of a geopolymer with an athermanous            additive; and        -   c) a geopolymer composite derived from geopolymer and            comprising athermanous additive,    -   and    -   ii) one or more non-brominated flame retardants selected from        -   a) phosphorus-based flame retardants,        -   b) nitrogen-based flame retardants, and        -   c) phosphorus/nitrogen-based flame retardants.

The composition may be in the form of an expandable granulate, whereinthe polymer is a vinyl aromatic polymer, the granulate furthercomprising one or more propellants. Preferably, the granulate isobtainable according to the process of the second aspect.

Preferably, the polymer is selected from vinyl polymer, polyurethane,polyolefin, polycarbonate, polyester, polyamide, polyimide, silicone andpolyether. More preferably, the polymer is selected from vinyl aromaticpolymer, polyethylene and polypropylene, most preferably the vinylaromatic polymer is polystyrene. The composition can be in the form ofexpandable vinyl aromatic polymer granulate, in the form of expandedvinyl polymer foam, or in the form of a masterbatch.

Further preferred is expandable vinyl aromatic polymer granulate, and anexpanded foam products made thereof, which comprises vinyl aromaticpolymer prepared from styrene monomer with optional incorporation of oneor more vinyl comonomers, and

-   -   a) 0.01-50 wt. % (by polymer weight, including solid and, if        any, liquid additives, but exclusive of propellant) of        geopolymer in powder form, with a particle size from 0.01 μm to        200 μm, measured using a Malvern Mastersizer apparatus according        to ISO 13320-1, and a BET surface in the range from 0.01 to        10000 m²/g, measured using a Gemini 2360 surface area analyzer        from Micromeritics according to ISO 9277:2010,    -   b) 0.01-50 wt. % (by polymer weight, including solid and, if        any, liquid additives, but exclusive of propellant) of a        combination of geopolymer with carbon blacks or mixture of at        least two types of carbon blacks. The ratio of geopolymer to        carbon black or mixtures of at least two carbon blacks is        typically in a range of from 1/100 to 100/1. The weight ratio of        first carbon black to the second, third or fourth carbon black        is typically in the range of from 1/100 to 100/1; with the same        ratio a mixture of second to third or third to fourth carbon        black is possible. A maximum of 10 different carbon blacks could        be used, in a respective ratio in the range of from 1/100 to        100/1,        and/or    -   c) 0.01-50 wt. % (by polymer weight, including solid and, if        any, liquid additives, but exclusive of propellant) of        geopolymer composite in powder form, with a particle size in a        range of from 0.01 μm to 200 μm, measured using a Malvern        Mastersizer apparatus according to ISO 13320-1, and a BET        surface in a range of from 0.01 to 10,000 m²/g, measured using a        Gemini 2360 surface area analyzer from Micromeritics according        to ISO 9277:2010.

Expandable vinyl aromatic polymer granulate may be expanded to form foamwith a uniform structure independently from the concentration ofgeopolymer or geopolymer composite in the foam. A uniform structure ischaracterized by the cell size distribution, as measured by astatistical analysis of the picture prepared by an optical microscopymeasurement.

Preferably, and according to the third aspect, the invention relates tothe expandable vinyl aromatic polymer granulate (particles) asobtainable according to the second aspect, preferably in an extrusion ora suspension processes.

The expandable vinyl aromatic polymer granulate comprises polymer, oneor more propellants, geopolymer additive i) and non-brominated flameretardants ii), where i) is a. geopolymer, or b. a combination of ageopolymer with an additive, but is preferably c. the geopolymercomposite as prepared from geopolymer and a suitable additive such asthose from the group of carbon based athermanous additives, withoptional modification of the geopolymer.

The vinyl aromatic polymer used in all aspects of the invention is inparticular polystyrene or a vinyl aromatic styrene copolymer. In thecopolymer, a part of styrene monomer is substituted with unsaturatedcomonomers, the reactivity of which is close to styrene monomer'sreactivity, such as p-methyl styrene and its dimers, vinyl toluene,t-butyl styrene or divinylbenzene. For the extrusion process andsuspension process, typically used vinyl aromatic polymers have adifferent number average molecular weight.

In the extrusion process, it is preferred to use a general purpose typeof polystyrene (or a copolymer with unsaturated styrene derivative) witha number average molecular weight (Mn) of from 40 to 100 kg/mol,preferably of from 50 to 80 kg/mol, more preferably of from 55 to 70kg/mol, and a suitable polydispersity of Mw/Mn in a range of from 2.0 to5.0, preferably of from 2.5 to 4.0, more preferably of from 3.0 to 3.5,and Mz/Mw in the range of from 1.5 to 2.5.

The vinyl aromatic polymer as produced in the suspension processpreferably has a number average molecular weight (Mn) from 50 to 120kg/mol, preferably of from 60 to 100 kg/mol, more preferably of from 70to 90 kg/mol, and a suitable polydispersity Mw/Mz in a range of from 2.0to 4.5, preferably from 2.5 to 4.0, more preferably from 3.0 to 4.0, andMz/Mw in the range of from 1.5 to 2.5.

The composition when in the form of expanded vinyl polymer foam has

-   -   a density of from 8 to 30 kg/m³, and    -   a thermal conductivity (as measured according to ISO 8301) of        from 25 to 35 mW/K·m).

Preferably, the expanded vinyl polymer is a vinyl aromatic polymer. Morepreferably, the foam is obtainable by expansion of the granulateaccording to the second aspect.

It is noted that, unlike the properties of the starting materials, theproperties of additives as contained in the granulate or foam arenotoriously difficult to determine. It is often considered moreappropriate to characterize the additives in granulate and foam withreference to the properties of the additives as initially used.

It is further noted that, whenever reference is made in the descriptionto an “additive”, this is in all embodiments and aspects of theinvention preferably a reference to an “athermanous additive”, asathermanous additives are most preferred additives.

The advantages of the present invention become apparent from thefollowing examples. Unless indicated otherwise, all percentages aregiven by weight.

Moreover, whenever reference is made in the description to an amount ofany additive “by weight of polymer”, this refers to the amount of theadditive by weight of polymer component inclusive of (solid and, if any,liquid) additives, but exclusive of propellant.

EXAMPLES

The below examples show a synergistic self-extinguishing effect in vinylaromatic polymer foams, when geopolymer composite was used incombination with common nitrogen-phosphorus flame retardants.

The following geopolymers were prepared with the process described below(Table 1).

TABLE 1 Geopolymer composites No. 1 2 3 Geopolymer matrix (wt. %) 5043.65 45 Ranco 9895 (wt. %) 50 43.65 45 Phosphoric acid (wt. %) − − 5Ammonium polyphosphate solution/ − 12.7  5 Exolit AP 420/(wt. %) Sodium(wt. %)    0.02  0.02 0.01 1^(st) filtration + + + Process water cakewashing + + + Demineralized water cake washing − + + Acidic washing withHCl solution (0.1%) + + + Repulpation in HCl acid solution (0.1%) + − −Repulpation in H₃PO₄ solution (1.5%) − − + Repulpation in APP solution− + − (7.6%) 2^(nd) filtration + + + Demineralized water cake washing +− − H₃PO₄ introduced via washing (1.5%) − − + APP introduced via washing(3%) − − +

Geopolymer Composite Preparation

The components: 39.6 kg of a powder mixture which comprises 19.8 kg ofmetakaolinite from C̆eské Lupkové Závody, a.s., Czech Republic, and 19.8kg of furnace slag from ironworks Katowice, Poland and 31.7 kg of sodiumwater glass with a molar module of 1.82 from Rudniki, Poland werecharged into a high speed screw conical mixer having a volume of 0.2 m³and were mixed over 1 min. with a speed of 300 rpm, to obtain athixotropic sol-gel. Then, the carbon additive, namely petroleum coke(Ranco 9895 from Richard Anton KG having a mean diameter particle sizeof 3 μm, a BET surface area of 28.5 m²/g, a total surface area of pores12.1 m²/g, and a sulphur content of 10100 ppm) was added in an amount of52 kg, and 46.8 l of water was added subsequently to the gel and mixedduring the next 1 min, also with a high speed of 300 rpm. After that,the viscous, homogenous gel was discharged from the mixer directly tothe open mould made of polished stainless steel in a total amount of 170kg. The mould was then closed and left for 24 h to performgeopolymerization. After 24 hours, the mould was opened and transportedto the drier to perform a drying process, for 8 h at a temperature of70° C., and for 16 h at a temperature of 120° C. Under these conditions,the geopolymer composite was dried over 24 h, and approx. 29 wt. % ofwater excess was evaporated from the material. Still approx. 10% ofwater remained in the material.

The dried geopolymer composite block was then placed into a crusher toobtain the granulate. The granulate with an average particles size of 10mm was jet milled with the use of hot air as milling medium, to obtainfree flowing powder.

The fine powder, containing about 3 wt. % of water (amount of approx.107 kg) was then placed in a 0.6 m³ in heated dissolver (reactor),equipped with a high speed agitator and a ribbon stirrer turning closelyto the dissolver walls. Immediately thereafter, 214 l of filtratedprocess water were charged into the dissolver and mixing was startedsimultaneously. An amount of 46.2 kg of concentrated aqueoushydrochloric acid (30%) was then over 5 min added to the reactor anddealkalization was performed. The starting pH, as measured before acidaddition, was 13, and after 60 min of mixing and dealkalization, thefinal pH was 7.5. The water (filtrate) having a conductivity of about80,000 μS/cm was filtrated from the powder of geopolymer composite and aprecipitate was obtained, containing approx. 50 wt. % of water. Then, aportion of process water was used to wash remaining sodium chloride andother chlorides from the precipitate. Washing was continued for 20 min,to obtain a filtrate having conductivity below 400 μS/cm. Alternatively,demineralized water could be used, reducing the filtrate conductivitybelow 300 μS/cm. To help destruct a thixotropic effect, the washing with0.1% hydrochloric acid solution could be performed after the wash withprocess or demineralized water. After that, a membrane squeeze of about16 bar was applied, to increase the solids content to 55 wt. %. Theprecipitate was removed from the press, granulated and loaded to arepulpation dissolver with the same mixing system as for thedealkalization reactor. Further salts elution in diluted solution ofhydrochloric acid (0.1%) and deionized water was performed. Followingrepulpation, the slurry was filtrated and washed for about 20 min, toobtain a filtrate with conductivity below 100 μS/cm.

Optionally, and to further improve self-extinguishing of vinyl aromaticfoams with the use of geopolymeric composite, 3 wt. % of a solution ofphosphoric acid (preferably 75% concentrated) in demineralized water maybe pumped through the filter press to modify the surface of geopolymeror geopolymer composite. The precipitate with water content of about 45wt. % was then finally vacuum dried over 4 h at a temperature 120° C.and pressure level of about 0.2 mbar. The dry precipitate, containing ofabout 10% of water and 5 wt. % of phosphoric acid in its structure, wasthen granulated and deagglomerated in an impact mill, to receive a finepowder with a D50 of about 2.7 μm as presented in FIG. 1. The 5 wt. %content of phosphoric acid was analysed in the geopolymer. The contentof analysed sodium was 200 ppm.

Alternatively, the geopolymer or geopolymer composite modification inthe repulpation step could be performed by creating 1-15% solutions withwater. Further, modification could be more sufficient if the solution ofH₃PO₄ or APP is used after demineralized water washing in the secondstep of membrane filtration. When the modification is done in therepulpation step, the washing step with the use of demineralized watermust be excluded in that case, so as to not elute the modifier.

In the end, a geopolymer composite (composite 1) powder with an averageparticles size (D50) of 2.7 μm is obtained, containing D90=5.9 μm,D99=10.1 μm (FIG. 1), BET 31.0 m²/g and total surface area of pores 17.5m²/g.

From all performed analyses of the quality of obtained geopolymers orgeopolymer composites, the sodium content is presented as the mostimportant one from an improved process point of view. It will be shownbelow how the sodium content and the phosphorus compound contentinfluence the foam's self-extinguishing properties, and to whichcontent, in the foam, brominated flame retardant could be reduced.

1. Sodium Analysis Description

A crucible with 0.05 g dried sample is placed in the oven for 5 h at500° C. for burning. The ash after burning is cooled down, in the nextstep ca. 10 ml deionized water with 1 ml HCl (35-38%) is added to thecrucible with sample, and the content is heated using a laboratoryhotplate at 140° C. for 30 min. The sample is cooled down andtransferred through the filter (cleaned beforehand for a minimum of 3times using deionized water) into the 100 ml flask, in the next step 8ml 1 M nitric acid with 4 ml spectral buffer of cesium chloride (2.5%Cs) is added. Simultaneously with the sample for analysis one control(blank) sample is prepared using the same procedure and the samereagents.

The sample solution as prepared applying the procedure described aboveis measured by Atomic Absorption Spectrometer, using a device AA iCE3500 GFS35Z, and following parameters: working mode: absorption, wavelength: 589.0 nm, gap: 0.2 nm,

The presented analytical procedure is based on the standard defining Naanalysis PN-ISO 9964-1:1994+Ap1:2009, sample preparation for measurementis based on internal procedure standard 61/A issue 3 dated 30 Apr. 2009.

2. Phosphorus Content

The content of H₃PO₄ and ammonium polyphosphate content were concludedfrom x-ray spectroscopy (XRF), by measuring the content of phosphorus,calculated as content of P₂O₅. XRF was performed with the use of avessel for powders and oils analysis on the Prolen foil with thicknessof 4 μm. A WD-XRF model S8 Tiger apparatus from Bruker was used toperform analysis.

3. Specific Surface Area

The specific surface area was determined using a Gemini 2360(Micromeritics) device. The measurement minimum of the Gemini 2360apparatus for specific surface was from 0.01 m²/g, the total surfacerange was from 0.1 to 300 m², and the pore size starting from 4.10⁻⁶cm³/g. Analysis was performed in a range P/P₀ from 0.05 to 0.3.Degasification of sample was made in an inert gas atmosphere of nitrogen(with flow of 50 cm³/min.). Later, the sample was dried over 2 h at atemperature of 110° C. Nitrogen was used as measurement gas.

4. Mercury Porosimetry

The pore size of the samples was measured using an Autopore IV 9500device according to an internal standard. Mercury contact angle is 130°.Before the measurement, each sample was conditioned for 2 h at 200° C.

Expandable Vinyl Aromatic Polymer Preparation

A mixture of vinyl aromatic polymer in the form of granules, containing0.5-5.0 wt. % of P/N flame retardant, 0.1 wt. % of bicumyl and 0.15 wt.% of nucleating agent (Polywax 2000), was dosed to the main hopper ofthe main 32D/40 mm twin-screw co-rotating extruder. The melt temperaturein main extruder was 180° C.

The geopolymer composite powder as prepared in EXAMPLE 1 in aconcentration of 10 wt. % was dosed to the side arm (54D/25 mm)twin-screw co-rotating extruder via two side feeders, and the vinylaromatic polymer (in the form of granules) was dosed to the main hopperof this extruder. The melt, containing 30 wt. % of concentratedgeopolymer additive, was transported to the main extruder. The melttemperature inside the extruder was 190° C.

The blowing agent (n-pentane/isopentane mixture 80/20%) was injected tothe main 32D/40 mm extruder downstream from the injection of the meltfrom the side twin-screw extruder. The concentration of blowing agentwas 5.5 wt. %, calculated on total mass of product.

The melt of vinyl aromatic polymer containing 0.5-5.0 wt. % of P/N flameretardant, bicumyl, nucleating agent, geopolymer composite and blowingagent was transported to the 30D/90 mm cooling extruder and pumpedthrough a 60 mm length static mixer, melt pump, screen changer, divertervalve and extruded through the die head with 0.75 mm diameter holes, andunderwater pelletized by the rotating knifes. Downstream, the roundedproduct, a granulate with a particle size distribution of 99.9% of thefraction 0.8-1.6 mm was centrifuged to remove the water, and was finallycoated by the suitable mixture of magnesium stearate with glycerinemonostearate and tristearate. The melt temperature in the coolingextruder was 170° C.

The coated beads were expanded, to measure the final general propertiesof expanded foam composite:

-   -   1. Thermal conductivity according to standard ISO 8301.    -   2. Mechanical properties (compressive and bending strength)        according to standard EN 13163.    -   3. Flammability according to tests methods: EN ISO 11925-2 and        DIN 4102 B2.    -   4. Dimensional stability under specified temperature and        humidity conditions of expanded foam were determined according        to standard PN-EN 1604+AC, which is normally used for XPS        materials.

The expandable granulate with a particle size distribution 0.8 to 1.6 mmwas in the pre-expander vessel treated for 50 sec. with steam having apressure of 0.2 kPa, and was then dried in a connected fluid bed drier.The obtained beads' density was 15 kg/m³. Then the expanded beads wereconditioned in a silo for 24 h and introduced to the block mould withdimensions of 1000×1000×500 mm. Steam having a pressure of 0.7 kPa wasused to weld the beads, and to obtain moulded blocks having a density of15.5 kg/m³. The mould cooling time in this case was 70 sec. The readyblock was cut into plates and then specimens taken after 6 days ofconditioning at room temperature.

Example 1 (Geopolymer Composite 1 Used)

This example is a comparative one, to show that geopolymer compositedoes not sufficiently act as effective flame retardant by itself. Theself-extinguishing test results as obtained are presented in Table 2.

Example 2 (Geopolymer Composite 1 Used)

This example is comparable with Example 1 and it gives reference thatalso a combination of synergist (bicumyl) and geopolymer composite doesnot give the required self-extinguishing properties for EPS foam. Theself-extinguishing test results as obtained are presented in Table 3.

Example 3 (No Geopolymer Composite Used)

This example is a comparative one, to show that addition of ammoniumpolyphosphate (only) in an amount of 2 wt. % is not sufficient to makeself-extinguished foams. The self-extinguishing test results as obtainedare presented in Table 4.

Example 4 (No Geopolymer Composite Used)

This example is comparable with Example 3, except that the ammoniumpolyphosphate content was increased up to 5 wt. %, to show that thisdoes not make a big difference in terms of the self-extinguishing effectin EPS foams. The self-extinguishing test results as obtained arepresented in Table 5.

Example 5 (Geopolymer Composite 1 Used)

This example is the first one with the use of geopolymer composite incombination with ammonium polyphosphate (2 wt. %). In this case for thefirst time a self-extinguishing effect was discovered. Theself-extinguishing test results as obtained are presented in Table 6.

Example 6 (Geopolymer Composite 1 Used)

This example is fully comparable with Example 5, and shows that anammonium polyphosphate content (5 wt. %) has the result of strengtheningthe self-extinguishing of EPS foam. It was the second example showing asynergistic effect between geopolymer composite and ammoniumpolyphosphate. The self-extinguishing test results as obtained arepresented in Table 7.

Example 7 (Geopolymer Composite 1 Used)

This example is comparable with Example 5. In this case instead addingof ammonium polyphosphate Exolite 422 (D50 17 μm), the grade Exolite 423(D50 8 μm) was added. It is shown that smaller particles of ammoniumpolyphosphate have a better surface contact with geopolymer composite,thus self-extinguishing of EPS foam was improved. The self-extinguishingtest results as obtained are presented in Table 8.

Example 8 (Geopolymer Composite 1 Used)

In this example, instead of ammonium polyphosphate,9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)/StruktolPolyphlox 3710/ was used, in an amount of 2 wt. %. This example iscomparable with examples 5 and 7 and shows that other types of P/N flameretardants can have a synergistic effect with geopolymer composite forself-extinguishing of EPS foam. The self-extinguishing test results asobtained are presented in Table 9.

Example 9 (Geopolymer Composite 2 Used)

This example is comparable with Example 5. It shows that, when ammoniumpolyphosphate (APP) is placed in the mezo-, microstructure of geopolymercomposite via wet method modification, the self-extinguishing effect ofEPS foam is strengthened significantly with the use of even lower amountof APP, in comparison to Example 5 or 7. The self-extinguishing testresults as obtained are presented in Table 10.

Example 10 (Geopolymer Composite 3 Used)

This example is comparable with Example 9 and shows that complex wetmodification with the use of phosphoric acid with ammonium polyphosphate(APP) (at separated stages of geopolymer composite preparation) and aswell addition to the polymer of D50 8 μm Exolite AP 433 in an amount of0.5 wt. % only can help to decrease the total amount of APP (moreexpensive then H₃PO₄) in ESP foam, while maintaining theself-extinguishing effect at the same level.

TABLE 2 DIN 4102 B2 Flame Flaming Maturing time height time Sample(days) (cm) (s) Dripping Ignition EXAMPLE 1 5 16.5 >20 2 YES 18.3 >20 2YES 18.4 >20 3 YES 19.1 >20 4 YES 18.1 >20 4 YES

TABLE 3 DIN 4102 B2 Flame Flaming Maturing time height time Sample(days) (cm) (s) Dripping Ignition EXAMPLE 2 5 11.2 >20 5 YES 13.5 >20 4NO 14.6 >20 6 NO 15.9 >20 8 NO 13.7 >20 3 NO

TABLE 4 DIN 4102 B2 Flame Flaming Maturing time height time Sample(days) (cm) (s) Dripping Ignition EXAMPLE 3 5 12.3 >20 2 YES 10.6 >20 1YES 14.0 >20 3 YES 0.0 0 0 NO 13.1 >20 3 YES

TABLE 5 DIN 4102 B2 Flame Flaming Maturing time height time Pater Sample(days) (cm) (s) Dripping ignition EXAMPLE 4 5 14.1 >20 0 NO 7.5 >20 0 NO0.0 0 0 NO 9.8 >20 2 YES 0.0 0 0 NO

TABLE 6 DIN 4102 B2 Flame Flaming Maturing time height time Pater Sample(days) (cm) (s) Dripping ignition EXAMPLE 5 5 5.0 >20 0 NO 0.0 0 0 NO8.4 >20 1 NO 0.0 0 0 NO 0.0 0 0 NO

TABLE 7 DIN 4102 B2 Flame Flaming Maturing time height time Pater Sample(days) (cm) (s) Dripping ignition EXAMPLE 6 5 0.0 0 0 NO 0.0 0 0 NO 0.00 0 NO 0.0 0 0 NO 0.0 0 0 NO

TABLE 8 DIN 4102 B2 Flame Flaming Maturing time height time Pater Sample(days) (cm) (s) Dripping ignition EXAMPLE 7 5 4.5 >20 0 NO 0.0 0 0 NO0.0 0 0 NO 0.0 0 0 NO 0.0 0 0 NO

TABLE 9 DIN 4102 B2 Flame Flaming Maturing time height time Pater Sample(days) (cm) (s) Dripping ignition EXAMPLE 8 5 3.6 9 0 NO 0.0 0 0 NO 0.00 0 NO 0.0 0 0 NO 0.0 0 0 NO

TABLE 10 DIN 4102 B2 Flame Flaming Maturing time height time PaterSample (days) (cm) (s) Dripping ignition EXAMPLE 9 5 0.0 0 0 NO 0.0 0 0NO 2.7 9 0 NO 0.0 0 0 NO 6.0 11 0 NO

TABLE 11 DIN 4102 B2 Flame Flaming Maturing time height time PaterSample (days) (cm) (s) Dripping ignition EXAMPLE 5 0.0 0 0 NO 10 0.0 0 0NO 0.0 0 0 NO 0.0 0 0 NO 0.0 0 0 NO

TABLE 12 Examples summary for prepared EPS foams. Examples 1 2 3 4 5 6 78 9 10 Synthos PS 585X YES YES YES YES YES YES YES YES YES YESGeopolymer composite (wt. %)/ 10/ 10/ — — 10/ 10/ 10/ 10/ 13/ 12.2/type/  1/  1/  1/  1/  1/  1/  2/ 3/  Phosphoric acid (wt. %) — — — — —— — — — 0.6* Exolit AP 420 (wt. %) — — — — — — — — 1.7* 0.6* Ammoniumpolyphosphate powder/ — — 2 5 2 5 — — — — Exolit AP 222 (D50 17 μm)/(wt. %) Ammonium polyphosphate powder/ — — — — — — 2 — — 0.5 Exolit AP223 (D50 8 μm)/ (wt. %) DOPO/ — — — — — — — 2 — — Struktol Polyphlox3710/(wt. %) Bicumyl (wt. %) — 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.150.15 Polywax 2000 (wt. %) 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.150.15 Pentane/Isopentane 80/20 (wt. %) 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.55.5 5.5 *means that phosphoric acid and/or ammonium polyphosphate wasincorporated into geopolymer composite structure via wet modificationmethod.

TABLE 13 Expanded foam composite parameters at ca. 15.0 kg/m³. Examples1 2 3 4 5 6 7 8 9 10 Dimensional stability at temp. 70° C. 0.10 0.100.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 and humidity 50 ± 5% (% of shapechange) Thermal conductivity (mW/m · K) 30.5 30.5 37.0 37.2 30.4 30.530.5 30.5 30.4 30.4 Flammability − − − − + + + + + + (EN standard)Flammability − − − − − + − + + + (DIN B2 standard) Compressive strengthat 10% def. 70 68 80 85 69 63 66 67 71 65 (kPa) Bending strength 140 137190 192 136 132 133 133 142 135 (kPa) Passed (+); Not passed (−)

1. Use of i) one or more geopolymer additives, wherein the geopolymeradditive is a) a geopolymer; b) a combination of a geopolymer with anathermanous additive; or c) a geopolymer composite derived fromgeopolymer and comprising athermanous additive, and ii) one or morenon-brominated flame retardants selected from a) phosphorus-based flameretardants, b) nitrogen-based flame retardants, and c)phosphorus/nitrogen-based flame retardants, for improving theself-extinguishing properties of a composition comprising vinyl aromaticpolymer.
 2. The use of claim 1, wherein the composition is expandablevinyl aromatic polymer granulate, or an expanded foam product madethereof, which composition comprises vinyl aromatic polymer preparedfrom styrene monomer with optional incorporation of one or more vinylcomonomers and c) 0.01-50 wt. % (by polymer weight, including solid and,if any, liquid additives, but exclusive of propellant) of geopolymercomposite in powder form, with a particle size in a range of from 0.01μm to 200 μm and a BET surface in a range of from 0.01 to 10,000 m²/g.3. The use of claim 1, wherein the composition does not comprisepolymeric brominated flame retardant, preferably wherein the compositiondoes not comprise brominated flame retardant, in particular wherein thecomposition does not comprise halogenated flame retardant.
 4. The use ofclaim 1, wherein the athermanous additive is one or more selected fromthe group consisting of (1) carbon-based athermanous additives, (2)metal athermanous additives, (3) metal oxide athermanous additives, and(4) metal sulfide athermanous additives.
 5. The use of claim 4, whereinthe carbon-based athermanous additive is selected from carbon black,coke, graphitized carbon black, graphite, graphite oxides, anthracite,graphene, and graphene oxide.
 6. The use of claim 4, wherein the metalathermanous additive is selected from copper, bismuth, nickel, iron,tungsten, silver, cadmium, cobalt, tin, zinc.
 7. The use of claim 4,wherein the metal oxide athermanous additive is selected from oxides ofthe metals of groups TIM, IV-VIIIA, and I-VB of the periodic table. 8.The use of claim 1, wherein the phosphorus-based flame retardant a) isselected from red phosphorus, organic and inorganic phosphates,phosphonates, phosphinates, and phosphoramidates, preferably wherein theorganic phosphate is selected from triphenyl phosphate (TPP), resorcinolbis(diphenylphosphate) (RDP), bisphenol A bis(diphenylphosphate) (BADP),tricresyl phosphate (TCP), and resorcinol bis(2,6-dixylenylphosphate)(RDX), the phosphinate is selected from aluminium phosphinates, calciumphosphinates and zinc phosphinates, and the phosphoramidate is9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).
 9. The use ofclaim 1, wherein the nitrogen-based flame retardant b) is selected fromhindered amine stabilizer, ammonium octamolybdate, melamineoctamolybdate, benzoguanamine, tris(hydroxyethyl) isocyanurate,allantois, glycoluril, melamine, melamine cyanurate, dicyandiamide,guanidine, carbodiimides, condensation products of melamine, andderivatives thereof.
 10. The use of claim 1, wherein thephosphorus/nitrogen-based flame retardant c) is selected from melaminephosphate, melamine pyrophosphate, melamine polyphosphate ammoniumpolyphosphate, and ethylene diamine phosphate.
 11. The use of claim 1,wherein the non-brominated flame retardant is a non-halogenated flameretardant.
 12. The use of claim 1, wherein the geopolymer or geopolymercomposite has been modified with one or more water-soluble compounds,preferably wherein the water-soluble compound is selected fromphosphorus compounds, nitrogen compounds, copper compounds, silvercompounds, zinc compounds, tin compounds, and magnesium compounds, morepreferably wherein the modification is with a phosphorus compound, inparticular wherein the modification is with a phosphorus compoundselected from phosphoric acid and ammonium polyphosphate.
 13. The use ofclaim 1, wherein the geopolymer or geopolymer composite has an averageparticle size (D50) in the range of 0.1 to 10 μm.
 14. A process for theproduction of expandable polymer granulate by an extrusion or asuspension process, the process comprising the addition of i) one ormore geopolymer additives, wherein the geopolymer additive is a) ageopolymer; b) a combination of a geopolymer with an athermanousadditive; or c) a geopolymer composite derived from geopolymer andcomprising athermanous additive, and ii) one or more non-brominatedflame retardants selected from a) phosphorus-based flame retardants, b)nitrogen-based flame retardants, and c) phosphorus/nitrogen-based flameretardants; wherein the polymer is a vinyl aromatic polymer. 15.Composition comprising one or more polymers, the composition furthercomprising i) one or more geopolymer additives, wherein the geopolymeradditive is a) a geopolymer; b) a combination of a geopolymer with anathermanous additive; or c) a geopolymer composite derived fromgeopolymer and comprising athermanous additive, and ii) one or morenon-brominated flame retardants selected from a) phosphorus-based flameretardants, b) nitrogen-based flame retardants, and c)phosphorus/nitrogen-based flame retardants, wherein the composition isin the form of an expandable granulate, wherein the polymer is a vinylaromatic polymer, the granulate further comprising one or morepropellants.
 16. Composition comprising one or more polymers, thecomposition further comprising i) one or more geopolymer additives,wherein the geopolymer additive is d) a geopolymer; e) a combination ofa geopolymer with an athermanous additive; or f) a geopolymer compositederived from geopolymer and comprising athermanous additive, and ii) oneor more non-brominated flame retardants selected from d)phosphorus-based flame retardants, e) nitrogen-based flame retardants,and f) phosphorus/nitrogen-based flame retardants, wherein thecomposition is in the form of expanded vinyl polymer foam, and the vinylpolymer is vinyl aromatic polymer, the foam having a density of from 8to 30 kg/m³, and a thermal conductivity (as measured according to ISO8301) of from 25 to 35 mW/K·m.
 17. The expanded vinyl polymer foam ofclaim 16, obtainable by expansion of a granulate, comprising acomposition comprising one or more polymers, the composition furthercomprising i) one or more geopolymer additives, wherein the geopolymeradditive is a) a geopolymer; b) a combination of a geopolymer with anathermanous additive; or c) a geopolymer composite derived fromgeopolymer and comprising athermanous additive, and ii) one or morenon-brominated flame retardants selected from a) phosphorus-based flameretardants, b) nitrogen-based flame retardants, and c)phosphorus/nitrogen-based flame retardants, wherein the composition isin the form of an expandable granulate, wherein the polymer is a vinylaromatic polymer, the granulate further comprising one or morepropellants.
 18. (canceled)